Seasonal oxygen isotope variations in freshwater bivalve shells as recorders of Amazonian rivers hydrogeochemistry.

Freshwater bivalve shell oxygen isotope values (δ18OS) may act as a recorder of river δ18O variations that can then be interpreted in terms of hydrology (e.g. precipitation-evaporation balance, precipitation and river discharge patterns). We investigated the potential of this proxy measured across the hinge of South American unionid shells: Anodontites elongatus collected in Peru and A. trapesialis in Brazil. The isotopic signatures were reproducible between individuals of the same species. A. trapesialis clearly showed a strong δ18OS cyclicity in accordance with its growth patterns while A. elongatus presented less clear δ18OS with lower amplitude. We confirm that the deposition of successive growth lines and increments is annual, with growth line corresponding to the wet season. Also, we suggest that low amplitude of δ18OS in the A. elongatus shells indicates a habitat close to the river while large amplitude of δ18OS cycles observed in A. trapesialis shells would reflect a floodplain lake habitat, seasonally disconnected from the river and thus subjected to higher seasonal fluctuations in water δ18O. Considering these promising first results, future studies could be directed towards the use of fossil shells to reconstruct the past and present hydrological and geochemical conditions of the Amazon.

A high-resolution history of the South American Monsoon from Last Glacial Maximum to the Holocene.

The exact extent, by which the hydrologic cycle in the Neotropics was affected by external forcing during the last deglaciation, remains poorly understood. Here we present a new paleo-rainfall reconstruction based on high-resolution speleothem δ18O records from the core region of the South American Monsoon System (SAMS), documenting the changing hydrological conditions over tropical South America (SA), in particular during abrupt millennial-scale events. This new record provides the best-resolved and most accurately constrained geochronology of any proxy from South America for this time period, spanning from the Last Glacial Maximum (LGM) to the mid-Holocene.

Geographical origin of Amazonian freshwater fishes fingerprinted by 87Sr/86Sr ratios on fish otoliths and scales.

Calcified structures such as otoliths and scales grow continuously throughout the lifetime of fishes. The geochemical variations present in these biogenic structures are particularly relevant for studying fish migration and origin. In order to investigate the potential of the (87)Sr/(86)Sr ratio as a precise biogeochemical tag in Amazonian fishes, we compared this ratio between the water and fish otoliths and scales of two commercial fish species, Hoplias malabaricus and Schizodon fasciatus, from three major drainage basins of the Amazon: the Madeira, Solimões, and Tapajós rivers, displaying contrasted (87)Sr/(86)Sr ratios. A comparison of the (87)Sr/(86)Sr ratios between the otoliths and scales of the same individuals revealed similar values and were very close to the Sr isotopic composition of the local river where they were captured. This indicates, first, the absence of Sr isotopic fractionation during biological uptake and incorporation into calcified structures and, second, that scales may represent an interesting nonlethal alternative for (87)Sr/(86)Sr ratio measurements in comparison to otoliths. Considering the wide range of (87)Sr/(86)Sr variations that exist across Amazonian rivers, we used variations of (87)Sr/(86)Sr to discriminate fish origin at the basin level, as well as at the sub-basin level between the river and savannah lakes of the Beni River (Madeira basin).

Human mobility on the Brazilian coast: an analysis of strontium isotopes in archaeological human remains from Forte Marechal Luz Sambaqui.

This study investigated strontium isotopes in the dental enamel of 32 human skeletons from Forte Marechal Luz sambaqui (shellmound), Santa Catarina, Brazil, aiming at identifying local and non-local individuals. The archeological site presents pot sherds in the uppermost archeological layers. Dental enamel was also examined from specimens of terrestrial fauna ((87)Sr/(86)Sr = 0.71046 to 0.71273) and marine fauna ((87)Sr/(86)Sr = 0.70917). The (87)Sr/(86)Sr isotope ratio for individuals classified as locals ranged from 0. 70905 to 0. 71064 and was closer to the isotope ratio of the seawater than to the ratio of the terrestrial fauna, indicating a strong influence of marine strontium on the inhabitants of this sambaqui. The results indicate the existence of three non-local individuals ((87)Sr/(86)Sr = 0.70761 to 0.70835), buried in both the level without pottery and the layer with pottery, possibly originated from the Santa Catarina Plateau, close to the municipality of Lages, or from the Curitiba Plateau. The occurrence of a slight difference between the isotope ratios of local individuals buried in the archeological layer without pottery, when compared to those in the layer with pottery, suggests a possible change in dietary patterns between these two moments in the site's occupation.

Human mobility on the Brazilian coast: an analysis of strontium isotopes in archaeological human remains from Forte Marechal Luz Sambaqui

This study investigated strontium isotopes in the dental enamel of 32 human skeletons from Forte Marechal Luz sambaqui (shellmound), Santa Catarina, Brazil, aiming at identifying local and non-local individuals. The archeological site presents pot sherds in the uppermost archeological layers. Dental enamel was also examined from specimens of terrestrial fauna (87Sr/86Sr = 0. 71046 to 0. 71273) and marine fauna (87Sr/86Sr = 0. 70917). The 87Sr/86Sr isotope ratio for individuals classified as locals ranged from 0. 70905 to 0. 71064 and was closer to the isotope ratio of the seawater than to the ratio of the terrestrial fauna, indicating a strong influence of marine strontium on the inhabitants of this sambaqui. The results indicate the existence of three non-local individuals (87Sr/86Sr = 0. 70761 to 0. 70835), buried in both the level without pottery and the layer with pottery, possibly originated from the Santa Catarina Plateau, close to the municipality of Lages, or from the Curitiba Plateau. The occurrence of a slight difference between the isotope ratios of local individuals buried in the archeological layer without pottery, when compared to those in the layer with pottery, suggests a possible change in dietary patterns between these two moments in the site's occupation.

O presente estudo investigou isótopos de estrôncio em esmalte dentário de 32 remanescentes humanos do sambaqui do Forte Marechal Luz, Santa Catarina, Brasil, com o objetivo de identificar indivíduos locais e não-locais. O sítio arqueológico apresenta fragmentos de cerâmica em suas camadas arqueológicas mais recentes. Além das amostras humanas, foram analisadas amostras de esmalte dentário de espécimes de fauna terrestre (87Sr/86Sr = 0,71046 a 0,71273) e fauna marinha (87Sr/86Sr = 0,70917). A razão 87Sr/86Sr dos indivíduos classificados como locais variou de 0,70905 a 0,71064, sendo próxima a razão de estrôncio existente nos oceanos e distante da razão obtida para a fauna terrestre do mesmo sítio, indicando uma influência marinha na origem do estrôncio dos habitantes desse sambaqui. Foram identificados de três indivíduos não locais (87Sr/86Sr = 0,70761 a 0,70835), sepultados em ambas camadas arqueológicas sem evidência e com evidência de cerâmica. Estes indivíduos podem ter origem no planalto catarinense, no entorno do município de Lages, ou do planalto curitibano. A ocorrência de uma pequena diferença entre as razões isotópicas dos indivíduos locais sepultados nas camadas sem evidência de cerâmica, daqueles sepultados nas camadas ceramistas, sugere a possibilidade de uma mudança nos padrões de alimentação entre esses dois momentos de ocupação do sítio.

Aneurismas e dissecçöes da aorta: progresso nos resultados imediatos do tratamento cirúrgico / Aneurysms and aortic dissections: progress in immediate results of surgical treatment

Após 1989, introduzimos algumas alteraçoes no tratamento cirúrgico dos aneurismas e dissecçoes da aorta, em nosso Serviço, entre elas maior rapidez no diagnóstico, uso de parada circulatória, hipotermia profunda, parada circulatória total, monitorizaçao hemodinâmica, controle dos distúrbios de coagulaçao, controle da pressao liquórica, implanataçao das artérias intercostais. Entre janeiro de 1980 e julho de 1994, 520 pacientes foram submetidos a tratamento cirúrgico de aneurismas ou dissecçoes da aorta, de foram consecutiva e nao selecionados. os pacientes foram divididos em três grupos, de acordo com o diagnóstico: Aneurisma de aorta ascendente (AAAS), Aneurisma de arco aórtico (AAAO), Dissecçao aguda da aorta tipos I e II (DAAO I e II). Nos três grupos, a mortalidade foi significativamente inferior para pacientes operados no período após 1989. Variáveis preditivas de mortalidade para AAAS foram: complicaçoes pulmonares (p = 0,0210), renais (p = 0,0310), neurológicas (p <0,0001). Para DAAO I e II, a hipertensao arterial (p < 0,0001), complicaçoes cardíacas (p < 0,0001), neurológicas (p < 0,0001), renais (p < 0,0001) e a rotura (p < 0,0001) foram preditivas de óbito, e para AAAO foram as variáveis: idade (p = 0,0001) e complicaçoes renais (p = 0,0015). Os autores concluem que as modificaçoes introduzidas no método de tratamento cirúrgico dos aneurismas e dissecçoes da aorta contribuíram significativamente para a melhora dos resultados.